GB2073610A

GB2073610A - Self-locking threaded articles

Info

Publication number: GB2073610A
Application number: GB8109965A
Authority: GB
Original assignee: Oakland Corp
Current assignee: Oakland Corp
Priority date: 1980-03-31
Filing date: 1981-03-31
Publication date: 1981-10-21
Also published as: DE3112631A1; US4325985A

Description

1

GB 2 073 610 A 1

SPECIFICATION Thread lock

5 The present invention is an improvement over my prior invention disclosed in my patents Serial Nos. 4,059,136, issued November 22,1977, and 4,081,012 issued March 28,1978.

In these prio r inventions, particu larly as it was ca r-10 ried out in commercial production, a series of threaded articles, typically bolts, was advanced while the bolts were suspended on a horizontally moving conveyor with the axes of the bolts vertical. The bolts were heated as they advanced to about 15 110°Fatwhichan uncured fluid resin, such as epoxy, was deposited on one side of the bolt and a fluid acitvator or hardener was deposited on the opposite side, and the two fluid deposits allowed to flow together. Where the two deposits met, there was an 20 interaction resulting in curing a thin barrier film of the resin which prevented further mixing of the resin and hardener.

The next step was to apply in fluid form a cover coat of a fluid material adapted to transform into a 25 thin rupturable protective film to protect the still-fluid deposits. The film forming fluid covering used in commercial practice was polyvinyl alcohol in a water solution. Since this covering material was required to dry sufficiently to permit removal of the 30 bolts from conveyor and to depositthem on a horizontally advancing belt, it was found necessary to raise temperature of the bolts to about 135°F before applying the film forming material. Thereafterthe temperature of the bolts was raised further as they 35 continued to advance on the conveyor while maintained with their axes vertical until they attained a temperature of about 160°F. At this time the PVAwas sufficiently dried to perm it the bolts to be deposited serially on a flat horizontally moving belt and there-40 afterthe bolts were maintained at a temperature of about 100°F, to complete drying of the fluid cover material to a thin, solid, dry non-tacky protective cover film, at which time the bolts were finished and could be stored or packaged in bulk without damage. 45 It was further found that when the uncured resin was a clear or unfilled epoxy resin, it was too fluid if deposited at 110° or brought to this temperature after deposit, so it was necessary to increase its viscosity by adding a filler, such as nylon powder, or 50 the like.

In practice the conveyor which advanced the bolts with their axes vertical past stations where the uncured resin and hardener and the protective cover material were applied was about twenty five feet 55 long, and the horizontal belt on which the bolts were deposited and advanced with their axes horizontal required a length of about one hundred feet.

In accordance with the present invention, much lower temperatures are permissible with very sub-60 stantial savings in energy, and in addition the space requirements of the equipment are greatly reduced. Where, as preferred the uncured resin is epoxy, it may be applied clear at temperatures not much above a typical room temperature. For example, it 65 and the hardener may be applied at90°F, and at this temperature a suitable clear or unfilled epoxy resin has a viscosity which allows flow around the thread grooves of the bolt from one side thereof into contact with the fluid hardener at the other side of the 70 bolt but is not sufficiently fluid to flow downwardly away from the point of deposit to leave an insufficient quantity of material atthe point of deposit.

This permits the addition of one of a mixture of powdered filler materials to the surface of the fluid 75 resin deposit at a subsequent station where the powder is seen to be in effect drawn into the fluid resin ratherthan remaining as a surface deposit thereon. A further important advantage is that in this case the filler material may comprise a mixture of 80 two or more different materials such as nylon powder, powdered glass, metal powders such as zinc, powdered graphite, table salt, and particulate material selected for imparting a desired color to the final deposit. It is difficult if not impossible to provide dif-85 ferent particulate material to the fluid resin before deposit of the resin and and to retain uniform dispersion of the particulate material through the resin, and maintain the desired proportions thereof. However, when the powders are mixed prior to applica-90 tion to the surface of the resin deposits, the powder proportions remain constant and the resin-powder proportions may be consistently controlled.

The addition of colored powder to previously deposited clear fluid resin, particularly epoxy resin, 95 to impart a desired color to the resin deposit results in a substantial improvement in appearance and color control overthe prior practice where the coloring agent was incorporated into the fluid resin, alone or with one or more particulate filler materials prior 100 to deposit of the resin on the bolts.

In the prior practice, where the protective cover coat was polyvinyl alcohol in an aqueous solution, the final film thickness overthe resin was less than that overthe hardener curing agent, because of the 105 affinity of the curing agent for water, and the water rejection ofthe resin. Accordingly, the application of the fluid cover coat required the use of a material whose viscosity, which controls the thickness of the deposited cover coat, catered to the worst condtion. 110 Accordingly, the protective cover film overthe curing agent produced a gel as a result of invasion of water ofthe fluid cover solution into the curing agent.

In accordance with the improved method dis-115 closed herein, a protective cover film is provided by applying in fluid phase a material which is transformed rapidly into a thin dry solid non-tacky protective film on exposure to ultra-violet radiation for a few seconds. This is initiated while the belt and resin 120 and curing agent deposits are at sufficiently low temperatures to permit the deposit of clear or unfilled fluid resin at a first station, the addition of a particulate material or a mixture of different particulate materials at a second station, followed by the appliThe drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

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GB 2 073 610 A

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cation of a fluid cover coat at a third station, all while the temperature ofthe components remains below 100°F, as for example, 90°F.

Immediately afterthe application ofthe fluid cover 5 coat, the bolts are subjected to ultra-violet radiation for a few seconds, which cures the cover coat into a thin, dry, solid, non-tacky film, while the fluid resin and curing agenttherefor remain fluid. Since the film-forming fluid material is transformed in a few 10 seconds to the solid protective film, this film is of substantially uniform thickness overthe resin and curing agent.

In a particular successful operation, the resin employed was clear or unfilled epoxy, the curing agent 15 was a fluid aliphatic amine, and the protective material was an alcohol solution of an ultra-violet sensitive, film forming material to be described below.

Figure 1 is a side elevation of the twin belt conveyor.

20 Figure 2 is a fragmentary sectional view on the line 2-2, Figure 1.

Figure 3 is a diagrammatical plan view ofthe apparatus.

Figure 4 is an enlarged fragmentary view of a por-25 tion of a bolt showing the resin deposit and protective film thereover.

Referring to the drawing, a series of bolts 10 are applied to a conveyor system comprising a pair of belts 12, between which the bolts are suspended by 30 the heads, as best seen in Figure 2. The complete system is diagrammatically shown in Figure 3. The conveyor belts 10 are moving in the direction ofthe arrow, and the individual bolts are supplied at a loading station A. At this loading station the belts are at 35 ambient temperature, which may be assumed to be about 70°F.

Preferably the temperature ofthe bolts is raised between stations A and B to about 90°F. This may be accomplished by electric heaters as indicated at 18. 40 AtB applicators 14and 16are provided atopposite sides ofthe advancing array of belts, for depositing controlled amounts ofthe epoxy resin and aliphatic amine curing agent. Applicators 14 and 16 may be of any suitable known type, and may for example be of 45 the type disclosed in my prior above identified patents. The fluid resin and curing agent have a viscosity such that they flow along the thread grooves into contact with each other, but remain essentially at the axially located zone of deposition, which may 50 extend for two or three threads along the bolt.

The bolts advance from station B to stations C and D without substantial change in temperature, which may be maintained if required by additional heaters (not shown). At station C any desired additives, such 55 as nylon particles, color particles, graphite or glass powder, crystals of ordinary table salt, powdered metals, particularly zinc, or mixtures of any of these in selected amounts. The particles are applied to the surfaces ofthe resin deposits by applicators 20, and 60 if desired may also be applied to the surfaces ofthe deposits of curing agents. As before noted, the particles appearto be drawn into the fluid deposits, and leave the surfacesthereof smooth and concavely curved as shown in Figure 4 at 22.

65 Immediately after deposition ofthe particulate matter, if such is desired, the bolts advance to station D, where a thin application of fluid film forming material is made, as for example by spraying from heads 24, located at both sides ofthe twin belts 12, shaped to direct the spray substantially uniformly overthe resin and curing agent deposits. The thin film formed thereby is illustrated at 24 in Figure 4.

The film forming material is immedately exposed to strong ultra-violet radiation at station E. The source of radiation is elongated UV radiating tubes 26, backed by reflectors, and positioned at both sides ofthe array of bolts 10, and below the twin belts 12. The ultra-violet light sources used are 8-12" tubes rated at 200 watts per inch. The rate of advance of the belts is such that the individual bolts are exposed to the radiation for only a few seconds, which is suf- £ ficientto convertthe surface coatings to extremely thin, solid, dry, non-tacky, protective cover films. It is noted that the ultra-violet radiation is effective to raise the temperature ofthe bolts, ofthe deposits thereon, to about 130°F, which is substantially maintained to the end at station G, where the finished bolts are deposited on a cross-belt 28. This is desirable, since it insures elimination of any remaining solvent from the film 24. The finished bolts are deposited randomly on belt 28, and the dry, non-tacky films 24 prevent finished bolts from sticking together.

The films 24 are produced by ultra-violet radiation on extremely thin (0.0005-0.0015 inches) coatings of film forming material dissolved in alcohol.

In general, UV curing coating compositions are initiated by a photochemical reaction. In general they are made up from an oligomeric resin (A), one or more monomers (B) and a photoinitiator system (C). In some coatings other types of coatings additives may also be included such as flow modifiers or surfactants, pigments, flame retardants, adhesion aids, stabilizers, gloss enhancers, flatting agents or others.

The oligomeric resins (A) which can be used are frequently liquids or readily liquefiable. They include alkyd resins, unsaturated polyester resins, unsaturated polyether resins, vinyl ester resins, vinyl ether resins, acrylic ester resins, acrylic ether resins, epoxy acrylate resins, curable epoxy resins, curable phenolic.resins, urethane acrylic resins or mixtures ofthe above. 5

The monomers (B) are materials which dilute or thin the coating and are also reactive to UV light to form a solid plastic. They also act as cross-linking * agents. These include chemical compounds which can be classified as acrylic esters, methacrylic esters, vinyl esters, vinyl ethers, acrylic ethers, allyl esters, allyl ethers, epoxides, styrene and substituted styrenes, vinyl pyrrolidone, acrylamide and substituted acrylamides, acrylonitrile, dienes.

The photoinitiators (C) can include aromatic ketones, halogenated aromatic ketones, benzoin ethers, alkyl aryl ketones, benzil ketals, oxime esters, halogenated thioxanthones, Onium salts, fluobo-rates, peroxides, azo free radical generators, and promotors like tertiary amine accelerators, organometallic complexes and mixture of the above.

The low viscosity UV curable coatings preferably

70

75

80

85

90

95

100

105

110

115

120

125

130

Claims

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GB 2 073 610 A

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have compositions in the ranges:

(A) 15-50%

(B) 80-50%

(C) 3-12%

5 Some examples of coatings formulations which are practical:

Parts by

Chemical Description of Component Weight

1. Vinyl polyesters of

10 bisphenal Afumarate 25 (A)

Styrene 15 (B)

Hydroxethyl methacrylate 29 (B)

Ethylene glycol dimethacrylate 15 (B)

Dimethylaminomethacrylate 10 (B)

15 Benzophenone 6 (C)

2. Acrylated glycidiyl ether of

20

bisphenyl A

20

(A)

Hexanediol diacrylate

45

(B)

Trimethylolpropane triacrylate

10

(B)

Vinyl acetate

5

(B)

Vinyl pyrrolidone

10

(B)

Diethoxyacetophenone

5

(C)

Triethanolamine

5

(C)

Acrylate polyurethane

15

(A)

Acrylated aliphatic glycidyl

ether

5

(A)

Tripropylene glycol diacrylate

20

(B)

Trimethylolpropanetriacrylate

10

(B)

Vinyl pyrrolidone

15

(B)

Vinyl versatate

25

(B)

Chloroalkyl aryl ketone

5

(C)

Amyl p-dimethylaminobenzoate

5

(C)

25

30

35 Excellent results have been achieved using the following composition forthe UV curable coverfilm:

Urethane Acrylate 600 (A)

Acrylated aliphatic glycidal ether 200 (A)

40 Tetra ethylene glycol diacrylate 700 (B)

Trimethylolpropanetriacrylate 450 (B)

Vinyl pyrrolidone 600 (B)

Vinyl versatate 750 (B)

45 Photo blend 300 (C)

Vinyl acetate 50 (B)

where the photo blend is composed of equal parts by weight of chloroalkyl aryl ketone, amyl p-dimethylaminobenzoate, and vinyl versatate. 50 In the foregoing the capital letters in parentheses following each component represents the appropriate category as described in the material preceding the tabulations.

Described in more general terms the invention 55 comprises the steps of depositing in the thread grooves of a bolt at circumferentially spaced stations a fluid resin and a fluid curing agenttherefor, applying a very thin fluid coating of an ultra-violet settable film-forming material over both of said deposits, and 60 hereafter initiating a brief high-intensity ultra-violet radiation ofthe fluid coating to transform into a thin continuous solid non-tacky, preferably transparent, protective film which covers the still-fluid deposits in the thread grooves ofthe bolt. Presumably the 65 above described steps are taken while the bolt is supported with its axis vertical. The fluid resin which is preferably an epoxy resin, has a viscosity at room temperature and up to about 100°F such that the deposit will flow circumferentially along the thread 70 grooves but will not flow downwardly in any substantial quantity. Accordingly the resin will remain in the axially located zone of deposition and the fluid resin deposit will flow circumferentially into contact with the circumferentially adjacent deposit of the 75 fluid curing agent. Any filter or other additives desired in the finished product are applied in powder form to the surface of the fluid resin deposit and in some cases to the deposit of the fluid curing agent. The temperature ofthe bolt and deposits is main-80 tained between room temperature and 100°F.

Up to the initiation ofthe ultra-violet radiation, preferably the temperature ofthe bolt is brought to about 90°F at the time ofthe deposition ofthe resin and curing agent.

85 The duration of the ultra-violet radiation is a very few seconds as for example less than ten seconds and preferably between two and five seconds. It is found that the ultra-violet radiation has the effect of somewhat raising at leastthe surface temperature of 90 the bolt and the fluid deposits to approximately 130°. This is desirable since the filming material is preferably applied in the form of an alcohol solution, and the elevation in temperature resulting from the ultraviolet radiation ensures substantially complete 95 elimination ofthe solvent. The raising ofthe temperature ofthe resin to about 130° is permissible because before this temperature is achived, the film-forming material has been transformed into a continuous solid protective film which retains the 100 fluid resin in position.

In some cases however it is desirable to reduce the temperature ofthe completed bolts before they are removed from the conveyor and deposited randomly on the receiving belt.

105 Where substantial amounts of particulate material have been incorporated into the resin, its viscosity is increased so that even without the protective film, no undesirable migration ofthe deposit would take place.

110 The present invention in commercial production results in a saving in overall power consumption of about 60%. In addition, the process avoids the high temperatures required in the prior methods. Finally, the present method permits a better control of addi-115 tion of additives to the resin, and an improvement in the appearance ofthe final produce.

While a general description and examples ofthe ultra-violet sensitive film-forming material is set forth, it will of course be understood that any com-120 position having the required physical properties and behavior as described herein may be employed. CLAIMS

1. The method of making a friction locking bolt of the type having in the thread grooves thereof cir-125 cumferentially adjacent deposits of an uncured fluid resin and a fluid curing agent therefor and a thin, non-tacky, rupturable solid protective film overlying said deposits which comprises depositing in the thread grooves ofthe bolt of cir-130 cumferentially spaced locations a fluid resin and a

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fluid curing agenttherefor, applying a very thin fluid coating of an ultra-violet settable film-forming material over both of said deposits,

and thereafter initiating a brief high-intensity 5 ultra-violet radiation ofthe fluid coating to transform the fluid coating into a thin, continuous, solid, non-tacky protective film which covers the still-fluid deposits in the thead grooves of the bolt.

2. The method as defined in claim 1, which com-10 prises supporting the bolt with its axis vertical during deposition ofthe fluid resin and curing agent> application ofthe fluid coating and radiation thereof; in which the fluid resin has a viscosity at ambient temperatures not exceeding 100°F which permits

15 flow of the resin along the thread grooves into contact with the curing agent while preventing substantial flow longitudinally ofthe bolt; and in which the deposition ofthe resin and curing agent, application ofthe film-forming material, and initiation ofthe 20 ultra-violet radiation all take place at temperatures not exceeding 100°F.

3. The method as defined in claim 2, in which the resin is an epoxy resin, and the deposit of resin and curing agent and application ofthe film-forming

25 material are accomplished at about 90°F.

4. The method as defined in claim 2, which comprises applying particulate material to the surface of the fluid resin before the application ofthe film-forming material thereto.

30 5. The method as defined in claim 3, which comprises applying particulate material to the surface of the fluid resin before the application ofthe film-forming material thereto.

6. The method as defined in claim 4, in which the 35 particulate material comprises one or more selected from group consisting of nylon powder, powdered glass, metal powders, powdered graphite, crystals of table salt, and powdered color-imparting material.

7. The method as defined in claim 5, in which the 40 particulate matter comprises one or more selected from group consisting of nylon powder, powdered glass, metal powders, powdered graphite, crystals of table salt, and powdered color-imparting material.

8. The method as defined in claim 1, in which the 45 film-forming material comprises a mixture by weight of 15-50% of an oligomeric resin, 50-80% of a monomer, and 3-12% of a photoinitiator system.

9. The method as defined in claim 8, in which the film-forming material has the composition, with

50 components given in parts by weight:

Components Parts by

Weight

Urethane Acrylate 600

Acrylated aliphatic glycidal 200 55 ether Tetra ethylene glycol diacrylate 700

Trimethylolpropanetriacrylate 450

Vinyl pyrrolidone 600

60 Vinyl versatate 750

Photo blend 300

Vinyl acetate 50

where the photo blend is composed of equal parts by weight of chloroalkyl aryl ketone, amyl 65 p-dimethylaminobenzoate, and vinyl versatate.

10. The method as defined in claim 2, in which the film-forming material comprises a mixture by weight of 15-50% of an oligomeric resin, 50-80% of a monomer, and 3-12% of a photoinitiator system.

70 11. The method as defined in claim 10, in which the film-forming material has the composition, with components given in parts by weight:

Components Parts by

Weight

75 Urethane Acrylate 600 Acrylated aliphatic glycidal ether 200 Tetra ethylene glycol diacrylate 700

80 Trimethylolpropanetriacrylate 450

Vinyl pyrrolidone 600

Vinyl versatate 750

Photo blend 300

Vinyl acetate 50

85 where the photo blend is composed of equal parts by weight of chloroalkyl aryl ketone, amyl p-dimethylaminobenzoate, and vinyl versatate.

12. The method as defined in claim 2, which comprises suspending a series of separate bolts

90 from an advancing conveyor, causing the bolts to traverse stations at which the resin and curing agent deposits are made, the film-forming material applied, and the ultra-violet radiation accomplished, and then removing the bolts serially from the con-

95 veyor and depositing the bolts randomly on a horizontal support surface.

13. The method as defined in claim 12, which comprises advancing a flat belt horizontally to provide the horizontal support surface for receiving the

100 bolts removed from the conveyor.

14. The method of making friction locking bolts which comprises suspending a series of bolts from an advancing conveyor, depositing a fluid resin at one side ofthe bolts as they advance and depositing

105 a fluid curing agenton the opposite side ofthe bolts as they advance, applying an ultra-violet curable fluid film-forming material overthe deposits as the bolts further advance, and subjecting the film-forming material to intense ultra-violet radiation as

110 the bolts further advance to form thin, continuous, solid, non-tacky protective films overthe still-fluid deposits thereon.

15. The method as defined in Claim 14, in which the fluid resin is art epoxy resin having a viscosity

115 suitable for deposition in the threads of bolts having their axes vertically disposed only at temperatures between ambienttemperature and about 100°F, and which comprises maintaining the bolts at the aforesaid range of temperatures during deposition

120 ofthe fluid resin and curing agents, application of the film-forming agent, and initiating ofthe ultra-violetradiation.

16. The method as defined in Claim 15, which comprises incidentally raising at leastthe surface

125 temperature ofthe bolts and the deposits to substantially above 100° during ultra-violet radiation, thereafter reducing the temperature ofthe products, and removing the products serially from the conveyor and depositing them randomly on a horizontal sup-

130 port surface.

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17. A method as claimed in Claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

18. A method as claimed in Claim 1 and carried 5 out using a UV-curable coating composition substantially as hereinbefore described in any one ofthe foregoing specific Examples.

19. Afriction lock element wherein adjacent areas of deposited uncured fluid resin and fluid cur-

10 ing agent overlying threaded surfaces at least in grooves thereof are retained and essentially sealed from the atmosphere by a thin protective film of UV-cured material applied overthe said threaded surfaces in uncured form and UV-cured in situ.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1981.

Published at the Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.